Objectively measured rheological patterns in artificial tears

Abstract

PurposeTo analyze the rheological behaviours of several artificial tears.MethodsIn vitro viscosity profile of the different artificial tears was obtained. A cone‐plate rotational rheometer was used with ascending and descending shear rate (from 1 s‐1 to 1000 s‐1, 330 measurements) at a constant temperature of 30°C and a fluid volume of 5 ml. The difference between viscosities in each section of shear rate was calculated.ResultsFour different rheological patterns were found in 78 artificial tears: shear‐thinning, shear‐thickening, thixotropic and Newtonian. Thixotropy was found between 0.17 and 104.576 mPas. Shear‐thinning, shear‐thickening and Newtonian behaviours showed a variation in viscosity in the last measurement section between −1.22 and 517 mPas.DiscussionThe viscosity of artificial tears always depends on the shear rate. It is possible to find two patterns simultaneously depending on the shear rate. These rheological patterns could serve to optimize the treatment with lubricants in different conditions of the ocular surface.ConclusionsThe variation of the shear rate conditions the viscous behavior of the fluids. We have defined four possible rheological models in the measured artificial tears. In vivo studies are necessary to evaluate the clinical utility of these findings.Bibliography Bhushan B. Introduction To Tribology. 2nd ed. New York: John Wiley & Sons, Inc; 2013. 711 p. Simmons PA, Aragona P, Wang H, Wang T. Physiochemical Properties of Hyaluronic Acid‐based Eye Drops. Montpellier, France; 2016. Lievens C, Berdy G, Douglass D, Montaquila S, Lin H, Simmons P, et al. Evaluation of an enhanced viscosity artificial tear for moderate to severe dry eye disease: A multicenter, double‐masked, randomized 30‐day study. Contact Lens Anterior Eye. 2019;42(4):443–9. Pult H, Tosatti SGP, Spencer ND, Asfour JM, Ebenhoch M, Murphy PJ. Spontaneous Blinking from a Tribological Viewpoint. Ocul Surf. 2015;13(3):236–49.